Benign prostatic hyperplasia or “BPH”, commonly referred to as an enlarged prostate, affects more than 50% of men over age 55 and is a worldwide problem. Approximately 200,000 surgeries to treat this condition are presently performed each year in the United States at a cost estimated at $1.6 billion annually. While pharmaceuticals, such as terazosin, may limit prostate growth for a period of time, eventually a surgical solution may be required.
The long standing surgical procedure for treating BPH is transurethral resection of the prostate or TURP, in which an electrosurgical loop heated by radiofrequency (“RF”) energy is moved to and fro within the prostate to resect (cut out) troughs of prostate tissue. While a TURP produces satisfactory voiding of urine, it requires general anesthesia and an hour or more of costly operating room time and entails up to 15% impotence, 5-10% permanent incontinence and bleeding requiring a transfusion in up to 10% of the patients. In addition, most TURP patients suffer from retrograde ejaculation, and up to 30% or more of TURP patients experience an infection or other adverse effect.
Recently, high powered RF roller ball devices have been introduced, which have somewhat reduced the bleeding and other adverse effects of a TURP. However, the use of RF roller ball devices requires general anesthesia and an hour or more of costly operating room time. Holmium lasers can be used for resection of the prostate, producing urine flow results equal to a TURP, while eliminating bleeding and most of the other adverse effects of the above described procedures using RF energy. However, Holmium laser resection typically requires one hour or more of expensive operating room time and general anesthesia.
The interstitial (within tissue) use of microwave, laser or RF energy to thermally coagulate a portion of the prostate, while taking less time and avoiding general anesthesia, does not significantly reduce the prostate's volume and thus produces less urine voiding relief than a TURP, high power RF roller ball or Holmium laser resection procedure. In addition, the patients treated with interstitial coagulating devices experience dysuria and discomfort for weeks after the procedure. If the tissue immediately underlying the urethra, which constitutes the exterior surface of the lobes of the prostate, is coagulated, the urethra dies, due to loss of its blood supply, leaving an open, irritating wound. The coagulated tissue then sloughs off and is excreted in the urine over a period of 3-6 weeks.
It would be desirable to be able to remove a sufficient amount of prostate tissue to provide immediate voiding and relief of BPH symptoms, while protecting the urethra and the immediately underlying tissue from damage, in a short, outpatient procedure, preferably in an outpatient treatment facility or a physician's office under local anesthesia and/or sedation.
Laser or RF energy can be used to coagulate a tumor, but coagulation occurs irregularly, as conduction of heat through tissue of differing densities and water content is not uniform. Consequently, it is necessary to closely observe the coagulation procedure to avoid damaging nearby blood vessels, nerves and other vital tissues. While a vaporization zone can be distinguished from normal tissue by ultrasound imaging, coagulated tissue cannot be differentiated from normal tissue by ultrasound imaging. As a result, expensive magnetic resonance imaging (MRI) equipment would be required to visually monitor the coagulation procedure, so that the process can be halted if the coagulation zone approaches important blood vessels, ducts, nerves or other tissues. Unhappily, the use of MRI equipment would increase the cost of an already expensive procedure.
It would be desirable to be able to accurately vaporize a tumor of any shape, while directing laser energy away from a vital blood vessel, duct, nerve or other tissue adjoining the tumor, with the ability to observe the vaporization process using a less costly ultrasound imaging system.